1. Field of the Invention
This invention relates to piers and walkways formed by concrete marine floats and, more particularly, to a system for fastening elongated wales along the upper side edges of the floats to connect the floats to each other.
2. Description of the Prior Art
Marine floats formed by a concrete casing surrounding a buoyant core are commonly used in marinas. Such floats are most commonly connected to each other by elongated, rigid wales extending along the upper side edges of the floats, with the wales bridging the junctions between adjacent floats. The wales are typically fastened to the floats by tie rods extending transversely through the float and projecting through the wales. The ends of the rods are threaded to receive conventional nuts and washers which are torqued against the wales to compress the wales against the float.
The above-described interconnecting system has proven satisfactory in protected locations. However, in waterways subjected to continual wave action of even small amplitudes, it is not possible to maintain the force of the wales against the floats.
It is important for the pressure between the wale and float to be maintained in order to prevent relative movement between the wale and float. Otherwise, the wales and possibly the floats may be quickly damaged.
Several factors are involved in loss of the clamping force of the wales on the float. The primary factor is shrinkage of the wales. The wales, being generally of wood, usually shrink to some extent as they dry. This shrinkage is often significant because the wood forming the wales is initially somewhat wet. Also, the wave action on the floats often causes the nuts to work loose from the ends of the tie rods. In an extreme case, the nuts can be completely removed from the through rods, and the through rods can project from the sides of the floats a large distance. This results in a hazardous boating condition since a boat or its occupant could become impaled on the projecting through rod.
Any movement between the wales and floats responsive to wave action wears away the inner surfaces of the wales, thus making subsequent tightening of the nuts without cracking the wale impossible.
The problems caused by nuts working loose from the ends of the tie rods usually be solved by the use of lock washers or jam nuts, although some problems still remain. For example, plastic inserts frequently used in lock nuts are often damaged by the rough surface of the tie rod threads as the nuts are torqued against the wales. This damage sometimes causes the nuts to lose their locking capability.
The primary problem, that of the shrinkage of the wales, is not as easily solved. Lock nuts and jam nuts do not, of course, compensate for the wood shrinkage. Spring-type nuts are capable of compensating for some shrinkage, but not of the magnitude encountered in the shrinkage of wooden wales. Neither is the use of large washers and extreme tightening of the nuts a solution. Wood fiber loading is normally limited to under 400 pounds per square inch in order to prevent crushing of the wales. The wales are not sufficiently resilient to fully compensate for shrinkage even when torqued to this extent. Also, the tension on the tie rods caused by tightening the nuts to this extent does not elongate the tie rod a sufficient distance to compensate for typical shrinking of the wales. While thinner, and hence more elastic, tie rods would undergo a greater elongation, thinner tie rods do not have sufficient strength to withstand the shear forces generated between the wales and the float. The final problem, namely, wearing of the wale inner surfaces, is essentially caused by non-correction of the first two problems, thus allowing greater relative movement between the wales and floats.
The only satisfactory solution for concrete floats subject to continuous wave action is the periodic tightening of the nuts. However, this solution is very labor intensive since it is only satisfactory if the force between the wale and float is always maintained. Otherwise, the wave action, which can exceed 40,000 cycles per day, can quickly wear a groove on the inside of the wale, which makes tightening the nut on the tie rod without damaging the wale impossible.
Attempts have been made to use steel wales to correct this problem. However, instead of the concrete float wearing away the wale, the steel wale often wears away the concrete float. The results are the same, a gap between the float and wale, and consequent damage.
Another technique for interconnecting a row of concrete marine floats dispenses with the use of wales entirely. This alternative technique utilizes pre-stressed or post-tensioned tendons running along the longitudinal axis of the row which compress the floats against each other end-to-end. This interconnection system also exhibits a number of problems and, if damaged by a storm or boat, requires the replacement of large sections instead of shorter, standard units. However, elongated post-tensioning does maintain the force of the floats against each other because the long length of the post-tensioning tendon allows sufficient elongation to compensate for the changes in the lengths of the floats. In other words, a longitudinal post-tensioned tendon one hundred times longer than a transverse post-tensioned tendon elongates one hundred times more than the transverse post-tensioned tendon for a given tension. Consequently, it is able to compensate for relative movements of its end points one hundred times greater.